/* ========================
   VARIABLES & RESET
   ======================== */
:root {
    --color-primary: #d41e3a;
    --color-dark: #1a1a1a;
    --color-light: #f5f5f5;
    --color-white: #ffffff;
    --color-gray: #666666;
    --color-success: #4caf50;
    --font-primary: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --transition: all 0.3s ease;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    background-color: var(--color-light);
    color: var(--color-dark);
    line-height: 1.6;
}

/* ========================
   LAYOUT
   ======================== */
.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ========================
   HEADER
   ======================== */
.header {
    background: linear-gradient(135deg, var(--color-dark) 0%, #2a2a2a 100%);
    color: var(--color-white);
    padding: 60px 20px;
    text-align: center;
    border-bottom: 4px solid var(--color-primary);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.header__title {
    font-size: 3.5rem;
    font-weight: 900;
    letter-spacing: -1px;
    margin-bottom: 10px;
    text-transform: uppercase;
}

.header__subtitle {
    font-size: 1.3rem;
    color: var(--color-primary);
    font-weight: 600;
}

/* ========================
   MAIN CONTENT
   ======================== */
main {
    min-height: calc(100vh - 300px);
    padding: 40px 20px;
}

/* ========================
   LANDING SECTION
   ======================== */
.landing {
    text-align: center;
    animation: fadeIn 0.5s ease;
}

.landing__content {
    background: var(--color-white);
    border-radius: 8px;
    padding: 50px 30px;
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.1);
}

.landing__content h2 {
    font-size: 2.5rem;
    margin-bottom: 20px;
    color: var(--color-dark);
    font-weight: 800;
}

.landing__content p {
    font-size: 1.1rem;
    color: var(--color-gray);
    margin-bottom: 40px;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* ========================
   CONTROLS
   ======================== */
.controls {
    display: flex;
    flex-direction: column;
    gap: 30px;
    align-items: center;
}

.difficulty-selector {
    width: 100%;
    max-width: 600px;
}

.difficulty-selector label {
    display: block;
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 15px;
    color: var(--color-dark);
}

.difficulty-buttons {
    display: flex;
    gap: 15px;
    justify-content: center;
    flex-wrap: wrap;
}

.difficulty-buttons input[type="radio"] {
    display: none;
}

.difficulty-buttons label {
    margin: 0;
    padding: 12px 24px;
    background-color: var(--color-light);
    border: 2px solid var(--color-dark);
    border-radius: 4px;
    cursor: pointer;
    font-weight: 600;
    font-size: 0.95rem;
    transition: var(--transition);
}

.difficulty-buttons input[type="radio"]:checked + label {
    background-color: var(--color-primary);
    color: var(--color-white);
    border-color: var(--color-primary);
}

.difficulty-buttons label:hover {
    background-color: #e8e8e8;
}

.difficulty-buttons input[type="radio"]:checked + label:hover {
    background-color: #c41830;
}

/* ========================
   BUTTONS
   ======================== */
.btn {
    font-family: var(--font-primary);
    font-size: 1rem;
    font-weight: 700;
    padding: 15px 40px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    transition: var(--transition);
    text-decoration: none;
    display: inline-block;
}

.btn--primary {
    background-color: var(--color-primary);
    color: var(--color-white);
    box-shadow: 0 4px 12px rgba(212, 30, 58, 0.3);
}

.btn--primary:hover {
    background-color: #c41830;
    box-shadow: 0 6px 18px rgba(212, 30, 58, 0.4);
    transform: translateY(-2px);
}

.btn--primary:active {
    transform: translateY(0);
    box-shadow: 0 2px 8px rgba(212, 30, 58, 0.3);
}

.btn--secondary {
    background-color: var(--color-gray);
    color: var(--color-white);
}

.btn--secondary:hover {
    background-color: #555555;
}

.btn--small {
    padding: 10px 20px;
    font-size: 0.9rem;
}

/* ========================
   WORKOUT SECTION
   ======================== */
.workout {
    animation: slideIn 0.4s ease;
}

.workout__header {
    background: linear-gradient(135deg, var(--color-dark) 0%, #2a2a2a 100%);
    color: var(--color-white);
    padding: 40px 30px;
    border-radius: 8px 8px 0 0;
    border-bottom: 4px solid var(--color-primary);
    margin-bottom: 30px;
}

.workout__header button {
    margin-bottom: 20px;
}

.workout__title {
    font-size: 2.5rem;
    font-weight: 900;
    margin-bottom: 10px;
    text-transform: uppercase;
}

.workout__tagline {
    font-size: 1.1rem;
    color: var(--color-primary);
    font-weight: 600;
    margin: 0;
}

.workout__content {
    background: var(--color-white);
    padding: 40px 30px;
    border-radius: 0 0 8px 8px;
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.1);
    margin-bottom: 30px;
}

.workout__description {
    background-color: var(--color-light);
    padding: 20px;
    border-left: 4px solid var(--color-primary);
    margin-bottom: 30px;
    border-radius: 4px;
    font-size: 1.1rem;
    line-height: 1.8;
}

.workout__level {
    display: inline-block;
    background-color: var(--color-primary);
    color: var(--color-white);
    padding: 8px 16px;
    border-radius: 4px;
    font-weight: 600;
    margin-bottom: 30px;
    font-size: 0.9rem;
}

/* ========================
   TIMER SECTION
   ======================== */
.timer-section {
    background: linear-gradient(135deg, #f5f5f5 0%, #eeeeee 100%);
    padding: 30px;
    border-radius: 8px;
    margin-bottom: 40px;
    text-align: center;
    border: 2px solid var(--color-primary);
}

.timer {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 20px;
}

.timer__display {
    font-size: 4rem;
    font-weight: 900;
    color: var(--color-primary);
    font-family: 'Courier New', monospace;
    letter-spacing: 2px;
}

.timer__controls {
    display: flex;
    gap: 15px;
    justify-content: center;
}

/* ========================
   INSTRUCTIONS
   ======================== */
.instructions {
    margin-bottom: 40px;
}

.instructions h3 {
    font-size: 1.5rem;
    font-weight: 800;
    margin-bottom: 20px;
    color: var(--color-dark);
}

.instructions__list {
    background-color: var(--color-light);
    padding: 25px 25px 25px 50px;
    border-radius: 4px;
    line-height: 2;
}

.instructions__list li {
    margin-bottom: 15px;
    color: var(--color-gray);
    font-size: 1rem;
}

.instructions__list li:last-child {
    margin-bottom: 0;
}

/* ========================
   EXERCISES
   ======================== */
.exercises {
    margin-bottom: 40px;
}

.exercises h3 {
    font-size: 1.5rem;
    font-weight: 800;
    margin-bottom: 20px;
    color: var(--color-dark);
}

.exercises__list {
    display: grid;
    gap: 15px;
}

.exercise-item {
    background-color: var(--color-light);
    padding: 20px;
    border-radius: 4px;
    border-left: 4px solid var(--color-primary);
}

.exercise-item__name {
    font-weight: 700;
    font-size: 1.1rem;
    color: var(--color-dark);
    margin-bottom: 8px;
}

.exercise-item__details {
    color: var(--color-gray);
    font-size: 0.95rem;
}

.exercise-item__notes {
    font-style: italic;
    color: #999;
    font-size: 0.9rem;
    margin-top: 8px;
}

/* ========================
   WORKOUT SUMMARY
   ======================== */
.workout__summary {
    background: linear-gradient(135deg, var(--color-primary), #c41830);
    color: var(--color-white);
    padding: 25px;
    border-radius: 4px;
    margin-top: 40px;
}

.summary-text {
    font-size: 1.1rem;
    font-weight: 600;
    margin: 0;
    line-height: 1.8;
}

/* ========================
   FOOTER
   ======================== */
.footer {
    background-color: var(--color-dark);
    color: var(--color-white);
    text-align: center;
    padding: 30px 20px;
    margin-top: 60px;
}

.footer p {
    margin: 0;
    font-size: 0.95rem;
}

/* ========================
   ANIMATIONS
   ======================== */
@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ========================
   RESPONSIVE DESIGN
   ======================== */
@media (max-width: 768px) {
    .header__title {
        font-size: 2.5rem;
    }

    .header__subtitle {
        font-size: 1rem;
    }

    .landing__content {
        padding: 30px 20px;
    }

    .landing__content h2 {
        font-size: 1.8rem;
    }

    .landing__content p {
        font-size: 1rem;
    }

    .workout__title {
        font-size: 1.8rem;
    }

    .difficulty-buttons {
        flex-direction: column;
    }

    .difficulty-buttons label {
        width: 100%;
    }

    .timer__display {
        font-size: 3rem;
    }

    .workout__content {
        padding: 25px 20px;
    }

    .workout__header {
        padding: 25px 20px;
    }

    .instructions__list {
        padding: 20px 20px 20px 40px;
    }

    .timer__controls {
        flex-wrap: wrap;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }

    .header__title {
        font-size: 2rem;
    }

    .header {
        padding: 40px 15px;
    }

    .landing__content h2 {
        font-size: 1.5rem;
    }

    .btn {
        width: 100%;
        max-width: 300px;
    }

    .workout__title {
        font-size: 1.5rem;
    }

    .timer__display {
        font-size: 2.5rem;
    }

    .timer__controls {
        width: 100%;
    }

    .timer__controls .btn {
        flex: 1;
    }
}